Multi-layer core golf ball

ABSTRACT

A golf ball comprising a core and a cover, wherein the core consists of: a solid inner core layer formed from an unfoamed thermoplastic composition and having a diameter of 1.10 inch or less and a center Shore C hardness (H center ) of 50 or less, one or more optional intermediate core layers, and an outer core layer formed from an unfoamed thermoset composition and having a thickness of 0.200 inches or greater and an outer surface Shore C hardness (H outer surface ) of 70 or greater, wherein H outer surface &gt;H center , and H outer surface −H center ≧40.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 13/958,854, filed Aug. 5, 2013, and also acontinuation-in-part of U.S. patent application Ser. No. 14/035,074,filed Sep. 24, 2013, the entire disclosures of which are herebyincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to multi-layer golf balls having a veryhigh positive gradient core, including a very soft, low compressioninner core layer formed from an unfoamed composition.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 8,182,368 to Kamino et al. discloses a golf ball whereinthe difference between the JIS-C hardness H4 of the core at its surfaceand the JIS-C hardness H3 of the core outer layer at its innermostportion is equal to or greater than 10.

U.S. Pat. No. 8,007,376 to Sullivan et al. discloses a golf ball havingan inner core layer with a negative hardness gradient and an outer corelayer with a positive hardness gradient.

U.S. Pat. No. 7,410,429 to Bulpett et al. discloses a golf ball whereinthe hardness of the inner core outer surface is the same as or lowerthan the hardness of the geometric center and the hardness of the outercore layer outer surface is greater than the hardness of the innersurface.

U.S. Pat. No. 6,695,718 to Nesbitt discloses a golf ball including acenter core component preferably formed from a sulfur-curedpolybutadiene and a core layer component preferably formed from aperoxide-cured polybutadiene and a metal salt of a fatty acid.

Despite these, and additional disclosures of golf balls having varioushardness gradient properties, there remains a need for a very highpositive gradient core, including a very soft, low compression innercore layer formed from an unfoamed composition. Such core would providegood durability while also contributing to spin reduction.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is directed to a golf ballcomprising a core and a cover. The core consists of an inner core layer,one or more optional intermediate core layers, and an outer core layer.The inner core layer is a solid layer formed from an unfoamedthermoplastic composition, and has a diameter of 1.10 inch or less and acenter Shore C hardness (H_(center)) of 50 or less. The outer core layeris formed from a thermoset composition, has a thickness of 0.200 inchesor greater, and an outer surface Shore C hardness (H_(outer surface)) of70 or greater. The outer surface hardness of the outer core layer is atleast 40 Shore C points greater than the center hardness of the innercore layer.

H_(center) may alternatively be 45 or less, or 40 or less, or less than40, or 35 or less, or less than 35, or 30 or less, or less than 30, or25 or less or less than 25, or 20 or less, or less than 20, or 15 orless, or less than 15, or 13 or less, or less than 13, or a Shore Chardness within a range having a lower limit of 5 or 10 and an upperlimit of 15 or 25 or 30 or 35 or 40.

The inner core layer may alternatively have a diameter of less than 1.10inches, or 1.00 inches or less, or less than 1.00 inches, or 0.90 inchesor less, or less than 0.90 inches, or 0.80 inches or less, or less than0.80 inches, or 0.75 inches or less, or less than 0.75 inches, or adiameter within a range having a lower limit of 0.10 or 0.15 or 0.20 or0.25 or 0.30 or 0.35 or 0.40 or 0.45 or 0.50 or 0.55 inches and an upperlimit of 0.60 or 0.65 or 0.70 or 0.75 or 0.80 or 0.85 or 0.90 or 0.95 or1.00 or 1.05 or 1.10 inches.

The inner core layer has an inner core outer surface having a Shore Chardness (H_(icos)) that differs from H_(center) by up to 5 Shore C. Inanother embodiment, H_(icos) and H_(center) differ by up to about 5Shore C. In one embodiment, H_(center) is greater than H_(icos) by up to5 Shore C. In another embodiment, H_(center) is less than H_(icos) by upto 5 Shore C. In other embodiments, H_(center) is greater than H_(icos)by up to 4 Shore C, or by up to 3 Shore C, or by up to 2 Shore C, or byless than 2 Shore C. Alternatively, H_(center) may be less than H_(icos)by up to 4 Shore C, or by up to 3 Shore C, or by up to 2 Shore C, or byless than 2 Shore C. In one embodiment, H_(center) and H_(icos) aresubstantially the same.

H_(outer surface) may alternatively be 75 or greater, or 70 or greater,or greater than 70, or 75 or greater, or greater than 75, 80 or greater,or greater than 80, or 85 or greater, or greater than 85, or 87 orgreater, or greater than 87, or 89 or greater, or greater than 89, or 90or greater, or greater than 90, or 91 or greater, or greater than 91, or92 or greater, or greater than 92, or a Shore C hardness within a rangehaving a lower limit of 80 or 85 or 87 or 89 and an upper limit of 90 or91 or 92 or 95.

In one embodiment, H_(outer surface) is greater than an outer core layerinner surface Shore C hardness (H_(inner surface)) by greater than 30.In another embodiment, H_(outer surface) is greater thanH_(inner surface) by from 10 to 30. In yet another embodiment,H_(outer surface) is greater than H_(inner surface) by less than 10.

The outer core layer may alternatively have a thickness of greater than0.10 inches, or 0.20 inches or greater, or greater than 0.20 inches, or0.30 inches or greater, or greater than 0.30 inches, or 0.35 inches orgreater, or greater than 0.35 inches, or 0.40 inches or greater, orgreater than 0.40 inches, or 0.45 inches or greater, or greater than0.45 inches, or a thickness within a range having a lower limit of 0.005or 0.010 or 0.015 or 0.020 or 0.025 or 0.030 or 0.035 or 0.040 or 0.045or 0.050 or 0.055 or 0.060 or 0.065 or 0.070 or 0.075 or 0.080 or 0.090or 0.100 or 0.200 or 0.250 inches and an upper limit of 0.300 or 0.350or 0.400 or 0.450 or 0.500 inches.

In another embodiment, H_(outer surface)−H_(center)≧45. In yet anotherembodiment, H_(outer surface)−H_(center)≧50. In still anotherembodiment, H_(outer surface)−H_(center)≧55. In an alternativeembodiment, H_(outer surface)−H_(center)≧55. In a different embodiment,H_(outer surface)−H_(center)≧60. In other embodiments,H_(outer surface)−H_(center)≧60, or H_(outer surface)−H_(center)−65, orH_(outer surface)−H_(center)>65, or H_(outer surface)−H_(center)≧70, orH_(outer surface)−H_(center)>70, or H_(outer surface)−H_(center)≧75, orH_(outer surface)−H_(center)>75, or H_(outer surface)−H_(center)≧80, orH_(outer surface)−H_(center)>80.

Additionally, the inner core layer has an inner core interface Shore Chardness (H_(inner core interface)). The interface hardness of a corelayer is defined herein as the extrapolated hardness from the curveproduced by making hardness measurements on the cross-section of a coreor ball radially outward from the center in about 2 mm increments. See,e.g., FIG. 1 and discussion below relating to FIG. 1.

The inner core layer has a negative hardness gradient wherein theinterface Shore C hardness of the inner core layer is less than thecenter Shore C hardness, or a zero hardness gradient wherein theinterface Shore C hardness of the inner core layer is within 1 Shore Cunit of the center Shore C hardness, or positive hardness gradientwherein the interface Shore C hardness of the inner core layer isgreater than the center Shore C hardness.

In a particular embodiment, the inner core layer has a center Shore Chardness (H_(center)) within a range having a lower limit of 1 or 5 or10 and an upper limit of 15 or 25 or 30 or 35 or 40 and an interfaceShore C hardness (H_(inner core interface)) within a range having alower limit of 5 or 10 or 15 and an upper limit of 15 or 20 or 25 or 30or 35 or 40 or 50, and has an overall zero hardness gradient whereinH_(inner core interface)=H_(center) or wherein−1<H_(inner core interface)−H_(center)<1; or a positive hardnessgradient wherein:

-   -   1<H_(inner core interface)−H_(center)<45,    -   or 1<H_(inner core interface)−H_(center)<15,    -   or 1<H_(inner core interface)−H_(center)<5.

For example, in one embodiment, 1<H_(inner core interface)−H_(center)≦5.In another embodiment, 2<H_(inner core interface)−H_(center)≦5. In yetanother embodiment, 3<H_(inner core interface)−H_(center)≦5. In analternative embodiment, 4<H_(inner core interface)−H_(center)≦5.

In other embodiments, the inner core layer may have an overall negativehardness gradient. For example, in one embodiment,−1>H_(inner core interface)−H_(center)≧−5. In yet another embodiment,−2>H_(inner core interface)−H_(center)≧−5. In still another embodiment,−3>H_(inner core interface)−H_(center)≧−5. In a different embodiment,−4>H_(inner core interface)−H_(center)≧−5.

In one embodiment, the outer core layer has an outer core interfaceShore C hardness (H_(outer core interface)) such thatH_(outer core interface)−H_(inner core interface)≦H_(outer surface)−H_(center).This occurs, for example, where: (i)H_(inner core interface)>H_(center), andH_(outer core interface)=H_(outer surface); (ii)H_(inner core interface)=H_(center), andH_(outer core interface)<H_(outer surface); (iii)H_(inner core interface)>H_(center), andH_(outer core interface)<H_(outer surface); and/or (iv)H_(inner core interface)=H_(center), andH_(outer core interface)=H_(outer surface).

A non-limiting example of (i) is where H_(outer core interface) (85Shore C)−H_(inner core interface) (50 Shore C)≦H_(outer surface)(85Shore C)−H_(center)(45 Shore C). In turn, an example of (ii) is whereH_(outer core interface) (80 Shore C)−H_(inner core interface) (50 ShoreC)≦H_(outer surface)(85 Shore C)−H_(center)(50 Shore C). And an exampleof (iii) is where H_(outer core interface) (80 Shore C)−H_(inner core)interface (55 Shore C)≦H_(outer surface)(85 Shore C)−H_(center)(50 ShoreC). Finally, one example of (iv) is where H_(outer core interface)(85Shore C)−H_(inner core interface)(50 Shore C)=H_(outer surface)(85 ShoreC)−H_(center)(50 Shore C).

In another embodiment,H_(outer core interface)−H_(inner core interface)>H_(outer surface)−H_(center).This occurs, for example, where: (v)H_(inner core interface)<H_(center), andH_(outer core interface)=H_(outer surface); (vi)H_(inner core interface)=H_(center), andH_(outer core interface)>H_(outer surface); or (vii)H_(inner core interface)<H_(center), andH_(outer core interface)>H_(outer surface).

A non-limiting example of (v) is where H_(outer core interface) (85Shore C)−H_(inner core interface) (45 Shore C)>H_(outer surface)(85Shore C)−H_(center)(50 Shore C). In turn, an example of (vi) is whereH_(outer core interface) (85 Shore C)−H_(inner core interface) (50 ShoreC)>H_(outer surface)(80 Shore C)−H_(center)(50 Shore C). And an exampleof (vii) is where H_(outer core interface) (85 Shore C)−H_(inner core)interface (45 Shore C)≦H_(outer surface)(80 Shore C)−H_(center)(50 ShoreC).

Non-limiting examples of suitable thermoplastic compositions include atleast one of ionomers; non-ionomeric acid polymers; polyurethanes,polyureas, and polyurethane-polyurea hybrids; polyester-basedthermoplastic elastomers; polyamides, copolymers of ionomer andpolyamide, polyamide-ethers, and polyamide-esters; ethylene-basedhomopolymers and copolymers; propylene-based homopolymers andcopolymers; triblock copolymers based on styrene and ethylene/butylene;derivatives thereof that are compatibilized with at least one grafted orcopolymerized functional group; and combinations thereof.

Suitable thermoset compositions include, for example, a rubber-basedcomposition comprising at least one of natural rubber, polybutadiene,polyisoprene, ethylene propylene rubber (EPR), ethylene-propylene-dienerubber (EPDM), styrene-butadiene rubber, butyl rubber, halobutyl rubber,polyurethane, polyurea, acrylonitrile butadiene rubber, polychloroprene,alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrilechlorinated isoprene rubber, polyalkenamer, phenol formaldehyde,melamine formaldehyde, polyepoxide, polysiloxane, polyester, alkyd,polyisocyanurate, polycyanurate, polyacrylate, and combinations thereof.

Optional intermediate core layers are disposed between the inner corelayer and outer core layer and have an individual layer thickness withina range having a lower limit of 0.005 or 0.010 or 0.015 or 0.020 or0.025 or 0.030 or 0.035 or 0.040 or 0.045 inches and an upper limit of0.050 or 0.055 or 0.060 or 0.065 or 0.070 or 0.075 or 0.080 or 0.090 or0.100 or 0.150 or 0.200 or 0.250 or inches. In one non-limitingembodiment, the core includes an intermediate layer formed from a rubbercomposition. In another non-limiting embodiment, the core includes anintermediate layer formed from an HNP composition. A core intermediatelayer may have a hardness in the range of from about 10 Shore C to about90 Shore C.

The multilayer core has an overall diameter of 1.00 inch or greater, or1.20 inches or greater, or 1.25 inches or greater, or 1.30 inches orgreater, or 1.35 inches or greater, or 1.40 inches or greater, or 1.45inches or greater, or 1.50 inches or greater, or 1.51 inches or greater,or 1.53 inches or greater, or 1.55 inches or greater, or an overalldiameter within a range having a lower limit of 0.50 or 0.70 or 0.75 or0.80 or 0.85 or 0.90 or 0.95 or 1.00 or 1.10 or 1.15 or 1.20 or 1.25 or1.30 or 1.35 or 1.40 or 1.45 or 1.50 or 1.51 or 1.53 or 1.55 and anupper limit of 1.55 or 1.60 or 1.61 or 1.62 or 1.63 or 1.64 inches.

The inner core layer has a compression of 40 or less, or 30 or less, or25 or less, or less than 25, or 20 or less, or less than 20, or 15 orless, or less than 15, or 10 or less, or less than 10, or 5 or less, orless than 5, or 0 or less, or less than 0. Meanwhile, the core has anoverall compression of 50 or greater, or 60 or greater, or 65 orgreater, or 70 or greater, or 80 or greater, or greater than 80, or 85or greater, or greater than 85, or 90 or greater, or an overallcompression within a range having a lower limit of 50 or 60 or 65 or 70or 80 or 85 and an upper limit of 90 or 95 or 100 or 110.

The inner core layer has a coefficient of restitution (“COR”) at 125ft/s of 0.780 or less, or 0.650 or less, or 0.600 or less, or 0.550 orless, and the multilayer core has an overall COR of 0.795 or greater, or0.800 or greater, or 0.810 or greater, or 0.815 or greater, or 0.820 orgreater.

Golf balls of the present invention typically have a COR of 0.700 orgreater, preferably 0.750 or greater, and more preferably 0.780 orgreater. Golf balls of the present invention typically have acompression of 40 or greater, or a compression within a range having alower limit of 50 or 60 and an upper limit of 100 or 120.

In one embodiment, a golf ball of the invention incorporates anintermediate layer (or inner cover layer) between the core and the cover(or between the core and outer cover layer). In such an embodiment, theintermediate layer or inner cover layer, formed about the core, has asurface hardness of from about 50 Shore D to about 80 Shore D.

The finished golf ball has a compression that is greater than acompression of the inner core layer and outer core layer, combined. Inone embodiment, the compression of the finished golf ball is greaterthan the compression of the inner core layer and outer core layer,combined, by at least 10%. In another embodiment, the compression of thefinished golf ball is greater than the compression of the inner corelayer and outer core layer, combined, by at least 15%. In yet anotherembodiment, the compression of the finished golf ball is greater thanthe compression of the inner core layer and outer core layer, combined,by at least 20%, or by at least 25%, or by at least 30%, or by at least35%, or by at least 40%, or by at least 50%, or by at least 55%, or byabout 60% or greater.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting core hardness as a function of distance fromthe center and further depicting extrapolated interfaces for the innerand outer core layers according to one embodiment of a golf ball of theinvention.

DETAILED DESCRIPTION

A golf ball of the invention produces a desired spin profile of reducedspin off the driver meanwhile maintaining moderate spin off wedges andirons. Several embodiments of a golf ball of the invention areillustrated in prophetic golf balls Ex. 1, Ex. 2, Ex. 3, and Ex. 4 andcompared with one conventional prophetic golf ball Comp. Ex. 1. In thisregard, at least one core layer in each of golf balls Ex. 1, Ex. 2, Ex.3, Ex. 4 and Comp. Ex. 1 includes at least one of the rubber-basedformulas set forth in TABLE I as follows:

TABLE I THERMOSET CORE MATERIALS INGREDIENTS Core Core Core (Phr)Formulation 1 Formulation 2 formulation 3 Polybutadiene 100 100 100 ZincOxide 5 5 5 Zinc diacrylate 35 38 31 (ZDA) Perkadox ® BC¹ 0.5 0.5 *Trigonox ® 265² * * 1 Antioxidant * * 0.4 ZnPCTP 0.5 0.5 0.5 ¹Perkadox ®BC is an initiating agent (Dicumyl peroxide) available from Akzo Nobel.²Trigonox ®265 is an initiating agent available from Akzo Nobel.

TABLE II below details the construction and certain properties forprophetic golf balls Ex. 1, Ex. 2, Ex. 3, Ex. 4 and Comp. Ex. 1:

TABLE II Golf Ball Construction & EXAMPLES Properties Ex. 1 Ex. 2 Ex. 3Ex. 4 Comp. Ex. 1 Inner Core Pebax ® Kraton ® Estane ® Elvax ® CoreMaterial 2533 SA 01³ D1101 K⁴ T370A TPU⁵ 40W⁶ Formulation 3⁷ Inner Core0.75 0.50 0.75 0.50 1.00 Diameter (in.) Center Hardness 47.6 29.2 36.412.5 71.0 (Shore C) Inner Core ≦40 ≦40 ≦40 ≦40 >40 Compression OuterCore Core Core Core Core Core Material Formulation FormulationFormulation Formulation Formulation 1⁷ 2⁷ 1 2 1 Outer Core 0.400 0.5250.400 0.525 0.275 Thickness (in.) Outer Core Surf. 87.9 88.6 88.1 89.287.5 Hardness (Shore C) Dual Core 77 68 65 52 88 CompressionIntermediate Surlyn ® Surlyn ® Surlyn ® Surlyn ® Surlyn ® Layer Material7940/8940⁸ 7940/8940 7940/8940 7940/8940 7940/8940 Intermediate 0.0350.035 0.035 0.035 0.035 Layer Thickness (in.) Intermediate 69.1 68.868.8 68.9 69.3 Layer Hardness (Shore D) Cover Material MDI⁹/ MDI/ MDI/MDI/ MDI/ PTMEG¹⁰/ PTMEG/ PTMEG/ PTMEG/ PTMEG/ E-300¹¹ E-300 E-300 E-300E-300 Cover Thickness (in.) 0.030 0.030 0.030 0.030 0.030 Cover Hardness82.1 81.9 82.0 82.2 82.1 (Shore C) Ball 86 78 76 61 99 Compression³Pebax ®2533 SA 01 is a thermoplastic elastomer formed from flexiblepolyether and rigid polyamide, available from ARKEMA (polyether amide).⁴Kraton ®D1101 K is a linear triblock copolymer based on styrene andbutadiene, with a styrene content of 31%, available from KRATON PolymersGroup (styrene block copolymer). ⁵Estane ®T370 A is a thermoplasticpolyurethane available from Lubrizol. ⁶Elvax ®40W is an ethylene vinylacetate copolymer resin available from DuPont (EVA). ⁷Core Formulations1, 2 & 3 are set forth in TABLE I above. ⁸Surlyn ®7940 (Li) andSurlyn ®8940 (Na), are medium acid, monovalent and medium flow ionomers.⁹Methylene diphenyl diisocyanate. ¹⁰Polytetramethylene ether glycol.¹¹Ethacure 300, dimethylthiotoluene diamine, sold by Albemarle.

As evident from TABLE I, core formulations 1, 2 & 3 differ from eachother in at least one of the amount of peroxide, the amount of zincdiacrylate, and presence/absence of an antioxidant.

Referring to golf balls Ex. 1, Ex. 2, Ex. 3, and Ex. 4 of TABLE II, eachincorporates a dual core comprising a very soft, low compression innercore layer surrounded by a hard higher compression thermoset outer corelayer. Additionally, each inner core layer has a diameter of less than1.10 inches, is formed from an unfoamed thermoplastic composition, andhas a center Shore C hardness of 50 or less. Meanwhile, each outer corelayer has a thickness of 0.200 inches or greater, is formed from athermoset composition, and has an outer surface Shore C hardness of 80or greater. Finally, in each of the dual cores of golf balls Ex. 1, Ex.2, Ex. 3, and Ex. 4, the outer core layer has an outer surface hardnessthat is at least 40 Shore C points greater than the center hardness ofthe inner core layer.

Specifically referring to golf ball Ex. 1, the inner core layer has adiameter of 0.75 in., is formed from a polyether amide, and has a centerShore C hardness of 47.6. The outer core layer meanwhile has a thicknessof 0.400 in., is formed from core formulation 1, and has an outersurface Shore C hardness of 87.9. The outer surface hardness of theouter core layer of golf ball Ex. 1 is therefore “at least 40 Shore Cpoints greater than the center hardness of the inner core layer” (namely40.3 Shore C points greater than the center hardness).

Golf ball Ex. 3's construction/composition is different than that golfball Ex. 1 in that the inner core layer of Ex. 3 is formed from athermoplastic polyurethane rather than a polyether amide. Severalproperty differences may also be noted between golf balls Ex. 3 and Ex.1, respectively: inner core layer center Shore C hardnesses (36.4 versus47.6); outer core layer surface Shore C hardnesses (88.1 versus 87.9);dual core compressions (65 versus 77); intermediate layer Shore Dhardnesses (68.8 versus 69.1); cover layer surface shore C hardness(82.0 versus 82.1); and golf ball compression (76 versus 86).Nevertheless, golf ball Ex. 3 has an outer core layer outer surfacehardness that is greater than the center hardness of the inner corelayer by 51.7 Shore C hardness points, which is well above “at least 40Shore C points greater”.

In turn, golf ball Ex. 4's construction/composition is different thanthat of golf ball Ex. 2 in that the inner core layer of Ex. 4 is formedfrom an EVA rather than a styrene block copolymer. Several propertydifferences may also be noted between golf balls Ex. 4 and Ex. 2,respectively: inner core layer center Shore C hardnesses (12.5 versus29.2); outer core layer surface Shore C hardnesses (89.2 versus 88.6);dual core compressions (52 versus 68); intermediate layer Shore Dhardnesses (68.9 versus 68.8); cover layer surface shore C hardness(82.2 versus 81.9); and golf ball compression (61 versus 78). Yet bothgolf balls Ex. 2 and Ex. 4 have a very high positive hardness gradientwherein the outer surface hardness of the outer core layer is at least40 Shore C points greater than the center hardness of the inner corelayer, namely by 59.4 and 76.7 Shore C hardness points, respectively.

Comparative golf ball Comp. Ex. 1, in contrast to golf balls Ex. 1, Ex.2, Ex. 3, and Ex. 4, is formed from a conventional thermosetrubber-based composition having a center Shore C hardness well above 50(namely 71). Additionally, Comp. Ex. 1 incorporates an outer core layerhaving an outer surface Shore C hardness that is not “at least 40 ShoreC points greater than the center hardness of the inner core layer” butrather, well below that, namely only 16.5 Shore C points greater.

Accordingly, each of golf balls Ex. 1, Ex. 2, Ex. 3, and Ex. 4incorporates a core having a steep positive Shore C hardness gradientprogressing from a hard core outer surface to a very soft center,whereas the core of golf ball Comp. Ex. 1 has a center Shore C hardnessabove 50 and a much more shallow Shore C hardness gradient from outersurface to center and well below “at least 40”.

It is to be understood that the examples herein are for illustrativepurposes only, and in no manner meant to limit the present invention.

FIG. 1 depicts interface hardnesses for the inner core layer and anouter core layer in one embodiment of a golf ball of the invention.Referring to FIG. 1, the interface hardnesses for each of the inner corelayer and outer core layer may be extrapolated from the curve producedby having made hardness measurements on the cross-section of the core orball radially outward from the center in about 2 mm increments. In FIG.1, the hardness results are plotted as a function of distance from thecore center (mm). As shown in FIG. 1, the center hardness is 48 Shore C,the outer surface hardness is 88 Shore C, and meanwhile, the inner corelayer interface hardness is 49 Shore C, and the outer core layerinterface hardness is 73 Shore C.

In a golf ball of the invention, the solid inner core layer is formedfrom an unfoamed composition selected from thermoplastic compositionsthat can be formulated to provide a very soft, low compression center.Non-limiting examples of suitable inner core layer materials includeRiteflex®425, Pebax® 2533 SA 01, Pebax® Rnew 25R53 SP 01, Kraton® D0243B, Kraton® D1101 A, Kraton® D1101 B, Kraton® D1101 K, Kraton® D1102 K,Kraton® D1118 B, Estane® S180A TPU, Estane® S385A TPU, Estane T370A TPU,Estane® UB400 TPU, Fusbond® 525D, Fusabond® C190, Nucrel® 9-1, Elvax®260, Elvax® 240W, Elvax® 150, and Elvax® 40W.

Thermoplastic compositions suitable for forming the inner core layerinclude ionomers; non-ionomeric acid polymers, such as E/Y- andE/X/Y-type copolymers, wherein E is an α-olefin (e.g., ethylene), Y is acarboxylic acid such as acrylic, methacrylic, crotonic, maleic, fumaric,or itaconic acid, and X is a softening comonomer such as vinyl esters ofaliphatic carboxylic acids wherein the acid has from 2 to 10 carbons,alkyl ethers wherein the alkyl group has from 1 to 10 carbons, and alkylalkylacrylates such as alkyl methacrylates wherein the alkyl group hasfrom 1 to 10 carbons; polyurethanes, polyureas, andpolyurethane-polyurea hybrids; polyester-based thermoplastic elastomers;polyamides, copolymers of ionomer and polyamide, polyamide-ethers, andpolyamide-esters; ethylene-based homopolymers and copolymers;propylene-based homopolymers and copolymers; triblock copolymers basedon styrene and ethylene/butylene; derivatives thereof that arecompatibilized with at least one grafted or copolymerized functionalgroup; and combinations of any two or more of the above thermoplasticpolymers.

Ionomers, including partially neutralized ionomers and highlyneutralized ionomers (HNPs), and ionomers formed from blends of two ormore partially neutralized ionomers, blends of two or more highlyneutralized ionomers, and blends of one or more partially neutralizedionomers with one or more highly neutralized ionomers, are particularlysuitable for forming the core layers. For purposes of the presentdisclosure, “HNP” refers to an acid copolymer after at least 80% of allacid groups present in the composition are neutralized. Preferredionomers are salts of E/X- and E/X/Y-type acid copolymers, wherein E isan α-olefin (e.g., ethylene), X is a C₃-C₈ α,β-ethylenically unsaturatedcarboxylic acid, and Y is a softening monomer. X is preferably selectedfrom methacrylic acid, acrylic acid, ethacrylic acid, crotonic acid, anditaconic acid. Methacrylic acid and acrylic acid are particularlypreferred. Y is preferably selected from (meth) acrylate and alkyl(meth) acrylates wherein the alkyl groups have from 1 to 8 carbon atoms,including, but not limited to, n-butyl (meth) acrylate, isobutyl (meth)acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate.Particularly preferred E/X/Y-type copolymers are ethylene/(meth) acrylicacid/n-butyl (meth) acrylate, ethylene/(meth) acrylic acid/isobutyl(meth) acrylate, ethylene/(meth) acrylic acid/methyl (meth) acrylate,and ethylene/(meth) acrylic acid/ethyl (meth) acrylate. As used herein,“(meth) acrylic acid” means methacrylic acid and/or acrylic acid.Likewise, “(meth) acrylate” means methacrylate and/or acrylate. Theα-olefin is typically present in the acid copolymer in an amount of 15wt % or greater, or 25 wt % or greater, or 40 wt % or greater, or 60 wt% or greater, based on the total weight of the acid copolymer. The acidis typically present in the acid copolymer in an amount of 6 wt % orgreater, or 9 wt % or greater, or 10 wt % or greater, or 11 wt % orgreater, or 15 wt % or greater, or 16 wt % or greater, or in an amountwithin a range having a lower limit of 1 or 4 or 5 or 6 or 8 or 10 or 11or 12 or 15 wt % and an upper limit of 15 or 16 or 17 or 19 or 20 or20.5 or 21 or 25 or 30 or 35 or 40 wt %, based on the total weight ofthe acid copolymer. The optional softening monomer is typically presentin the acid copolymer in an amount within a range having a lower limitof 0 or 1 or 3 or 5 or 11 or 15 or 20 wt % and an upper limit of 23 or25 or 30 or 35 or 50 wt %, based on the total weight of the acidcopolymer.

The acid copolymer is at least partially neutralized with a cationsource, optionally in the presence of a high molecular weight organicacid, such as those disclosed in U.S. Pat. No. 6,756,436, the entiredisclosure of which is hereby incorporated herein by reference. The acidcopolymer can be reacted with the optional high molecular weight organicacid and the cation source simultaneously, or prior to the addition ofthe cation source. Suitable cation sources include, but are not limitedto, metal ion sources, such as compounds of alkali metals, alkalineearth metals, transition metals, and rare earth elements; ammonium saltsand monoamine salts; and combinations thereof. Preferred cation sourcesare compounds of magnesium, sodium, potassium, cesium, calcium, barium,manganese, copper, zinc, lead, tin, aluminum, nickel, chromium, lithium,and rare earth metals.

Suitable ionomers are further disclosed, for example, in U.S. PatentApplication Publication Nos. 2005/0049367, 2005/0148725, 2005/0020741,2004/0220343, and 2003/0130434, and U.S. Pat. Nos. 5,587,430, 5,691,418,5,866,658, 6,100,321, 6,562,906, 6,653,382, 6,756,436, 6,777,472,6,762,246, 6,815,480, 6,894,098, 6,919,393, 6,953,820, 6,994,638,7,375,151, and 7,652,086, the entire disclosures of which are herebyincorporated herein by reference.

Thermoplastic compositions of the present invention optionally includeadditive(s) and/or filler(s) in an amount of 50 wt % or less, or 30 wt %or less, or 20 wt % or less, or 15 wt % or less, based on the totalweight of the thermoplastic composition. Suitable additives and fillersinclude, but are not limited to, chemical blowing and foaming agents,optical brighteners, coloring agents, fluorescent agents, whiteningagents, UV absorbers, light stabilizers, defoaming agents, processingaids, antioxidants, stabilizers, softening agents, fragrance components,plasticizers, impact modifiers, TiO₂, acid copolymer wax, surfactants,performance additives (e.g., A-C® performance additives, particularlyA-C® low molecular weight ionomers and copolymers, A-C® oxidizedpolyethylenes, and A-C® ethylene vinyl acetate waxes, commerciallyavailable from Honeywell International Inc.), fatty acid amides (e.g.,ethylene bis-stearamide and ethylene bis-oleamide), fatty acids andsalts thereof (e.g., stearic acid, oleic acid, zinc stearate, magnesiumstearate, zinc oleate, and magnesium oleate), and fillers, such as zincoxide, tin oxide, barium sulfate, zinc sulfate, calcium oxide, calciumcarbonate, zinc carbonate, barium carbonate, tungsten, tungsten carbide,silica, lead silicate, clay, mica, talc, nano-fillers, carbon black,glass flake, milled glass, flock, fibers, and mixtures thereof. Suitableadditives are more fully described in, for example, U.S. PatentApplication Publication No. 2003/0225197, the entire disclosure of whichis hereby incorporated herein by reference. In a particular embodiment,the total amount of additive(s) and filler(s) present in thethermoplastic composition is 20 wt % or less, or 15 wt % or less, or 12wt % or less, or 10 wt % or less, or 9 wt % or less, or 6 wt % or less,or 5 wt % or less, or 4 wt % or less, or 3 wt % or less, or within arange having a lower limit of 0 or 2 or 3 or 5 wt %, based on the totalweight of the thermoplastic composition, and an upper limit of 9 or 10or 12 or 15 or 20 wt %, based on the total weight of the thermoplasticcomposition. In a particular aspect of this embodiment, thethermoplastic composition includes filler(s) selected from carbon black,micro- and nano-scale clays and organoclays, including (e.g., Cloisite®and Nanofil® nanoclays, commercially available from Southern ClayProducts, Inc.; Nanomax® and Nanomer® nanoclays, commercially availablefrom Nanocor, Inc., and Perkalite® nanoclays, commercially availablefrom Akzo Nobel Polymer Chemicals), micro- and nano-scale talcs (e.g.,Luzenac HAR® high aspect ratio talcs, commercially available fromLuzenac America, Inc.), glass (e.g., glass flake, milled glass,microglass, and glass fibers), micro- and nano-scale mica and mica-basedpigments (e.g., Iriodin® pearl luster pigments, commercially availablefrom The Merck Group), and combinations thereof. Particularly suitablecombinations of fillers include, but are not limited to, micro-scalefiller(s) combined with nano-scale filler(s), and organic filler(s) withinorganic filler(s).

Examples of commercially available thermoplastics suitable for formingthe inner core layer include, but are not limited to, Surlyn® ionomerresins, Hytrel® thermoplastic polyester elastomers, ionomeric materialssold under the trade names DuPont® HPF 1000 and HPF 2000, Nucrel® acidcopolymer resins, Fusabond® metallocene-catalyzed polyethylenes,Fusabond® functionalized ethylene acrylate copolymers, Fusabond®functionalized ethylene vinyl acetate copolymers, Fusabond® anhydridemodified HDPEs, Fusabond® random ethylene copolymers, Fusabond®chemically modified ethylene elastomers, and Fusabond® functionalizedpolypropylenes, all of which are commercially available from E. I. duPont de Nemours and Company; Iotek® ionomers, commercially availablefrom ExxonMobil Chemical Company; Amplify® IO ionomers of ethyleneacrylic acid copolymers, commercially available from The Dow ChemicalCompany; Clarix® ionomer resins, commercially available from A. SchulmanInc.; Elastollan® polyurethane-based thermoplastic elastomers,commercially available from BASF; Pebax® thermoplastic polyether andpolyester amides, Lotader® ethylene/acrylic ester/maleic anhydriderandom terpolymers and Lotader® ethylene/ethyl acrylate/maleic anhydriderandom terpolymers, all of which are commercially available from ArkemaInc.; Kraton® linear triblock copolymers based on styrene andethylene/butylene, commercially available from Kraton PerformancePolymers Inc.; and Riteflex® polyester elastomers, commerciallyavailable from Ticona.

The inner and outer core layers are formulated to have differentproperties and they are formed from different types of compositions. Forexample, the inner core layer may be formed from an ionomer compositionand the outer core layer is formed from a polybutadiene composition.Thermoset rubber compositions suitable for forming the outer core layerare those that can be formulated to provide an outer core surfacehardness such that the core has an overall very high positive hardnessgradient of at least 40 Shore C.

The outer core layer core may be made from a composition including atleast one thermoset base rubber, such as a polybutadiene rubber, curedwith at least one peroxide and at least one reactive co-agent, which canbe a metal salt of an unsaturated carboxylic acid, such as acrylic acidor methacrylic acid, a non-metallic coagent, or mixtures thereof.Preferably, a suitable antioxidant is included in the composition. Anoptional soft and fast agent (and sometimes a cis-to-trans catalyst),such as an organosulfur or metal-containing organosulfur compound, canalso be included in the core formulation.

The degree of crosslinking of the rubber may be increased by increasingthe amount (phr) of peroxide added. Meanwhile, zinc diacrylate is acoagent commonly used with peroxide to increase the state of cure, totake part in the cross-linking of polybutadiene. A small amount of ZDAand/or ZDMA produces a golf hall core with lower initial velocity andlower compression than a larger amount of coagent. The use of ZDAcoagent may increase velocity and hardness and contribute to a hardfeel. Thus, the amount of peroxide initiator and coagent can be variedto achieve a desired hardness. Antioxidants are compounds that inhibitor prevent the oxidative breakdown of elastomers, and/or inhibit orprevent reactions that are promoted by oxygen radicals.

Other ingredients that are known to those skilled in the art may beused, and are understood to include, but not be limited to,density-adjusting fillers, process aides, plasticizers, blowing orfoaming agents, sulfur accelerators, and/or non-peroxide radicalsources. The base thermoset rubber, which can be blended with otherrubbers and polymers, typically includes a natural or synthetic rubber.A preferred base rubber is 1,4-polybutadiene having a cis structure ofat least 40%, preferably greater than 80%, and more preferably greaterthan 90%. Examples of desirable polybutadiene rubbers include BUNA® CB22and BUNA® CB23, commercially available from LANXESS Corporation; UBEPOL®360L and UBEPOL® 150L and UBEPOL-BR rubbers, commercially available fromUBE Industries, Ltd. of Tokyo, Japan; BUDENE 1208, 1207, commerciallyavailable from Goodyear of Akron, Ohio; and CB BUNA® 1203G1, 1220, and1221, commercially available from LANXESS Corporation; Europrene®NEOCIS® BR 40 and BR 60, commercially available from Polimeri Europa;and BR 01, BR 730, BR 735, BR 11, and BR 51, commercially available fromJapan Synthetic Rubber Co., Ltd; and KARBOCHEM® ND40, ND45, and ND60,commercially available from Karbochem.

The base rubber may also comprise high or medium Mooney viscosityrubber, or blends thereof. A “Mooney” unit is a unit used to measure theresistance to flow of raw or unvulcanized rubber. The viscosity in a“Mooney” unit is equal to the torque, measured on an arbitrary scale, ona disk in a vessel that contains rubber at a temperature of 100° C. androtates at two revolutions per minute. The measurement of Mooneyviscosity is defined according to ASTM D-1646.

The Mooney viscosity range is preferably greater than about 40, morepreferably in the range from about 40 to about 80 and more preferably inthe range from about 40 to about 60. Polybutadiene rubber with higherMooney viscosity may also be used, so long as the viscosity of thepolybutadiene does not reach a level where the high viscositypolybutadiene adversely interferes with the manufacturing machinery. Itis contemplated that polybutadiene with viscosity less than 65 Mooneycan be used with the present invention.

In one embodiment of the present invention, golf ball cores made withmid- to high-Mooney viscosity polybutadiene material exhibit increasedresiliency (and, therefore, distance) without increasing the hardness ofthe ball. Such cores are soft, i.e., compression less than about 60 andmore specifically in the range of about 50-55. Cores with compression inthe range of from about 30 about 50 are also within the range of thispreferred embodiment.

Commercial sources of suitable mid- to high-Mooney viscositypolybutadiene include LANXESS CB23 (Nd-catalyzed), which has a Mooneyviscosity of around 50 and is a highly linear polybutadiene. If desired,the polybutadiene can also be mixed with other elastomers known in theart, such as other polybutadiene rubbers, natural rubber, styrenebutadiene rubber, and/or isoprene rubber in order to further modify theproperties of the core. When a mixture of elastomers is used, theamounts of other constituents in the core composition are typicallybased on 100 parts by weight of the total elastomer mixture.

In one preferred embodiment, the base rubber comprises an Nd-catalyzedpolybutadiene, a non-rare earth-catalyzed polybutadiene rubber, orblends thereof. If desired, the polybutadiene can also be mixed withother elastomers known in the art such as natural rubber, polyisoprenerubber and/or styrene-butadiene rubber in order to modify the propertiesof the core. Other suitable base rubbers include thermosetting materialssuch as, ethylene propylene diene monomer rubber, ethylene propylenerubber, butyl rubber, halobutyl rubber, hydrogenated nitrile butadienerubber, nitrile rubber, and silicone rubber.

Thermoplastic elastomers (TPE) may also be used to modify the propertiesof the core layers, or the uncured core layer stock by blending with thebase thermoset rubber. These TPEs include styrenic block copolymers,such as styrene ethylene butadiene styrene, styrene-isoprene-styrene,etc., a metallocene or other single-site catalyzed polyolefin such asethylene-octene, or ethylene-butene, or thermoplastic polyurethanes(TPU), including copolymers. Other suitable TPEs for blending with thethermoset rubbers of the present invention include PEBAX®, which isbelieved to comprise polyether amide copolymers, HYTREL®, which isbelieved to comprise polyether ester copolymers, thermoplastic urethane,and KRATON®, which is believed to comprise styrenic block copolymerselastomers. Any of the TPEs or TPUs above may also contain functionalitysuitable for grafting, including maleic acid or maleic anhydride.

Additional polymers may also optionally be incorporated into the baserubber. Examples include, but are not limited to, thermoset elastomerssuch as core regrind, thermoplastic vulcanizate, copolymeric ionomer,terpolymeric ionomer, polycarbonate, polyamide, copolymeric polyamide,polyesters, polyvinyl alcohols, acrylonitrile-butadiene-styrenecopolymers, polyarylate, polyacrylate, polyphenylene ether,impact-modified polyphenylene ether, high impact polystyrene, diallylphthalate polymer, styrene-acrylonitrile polymer (SAN) (includingolefin-modified SAN and acrylonitrile-styrene-acrylonitrile polymer),styrene-maleic anhydride copolymer, styrenic copolymer, functionalizedstyrenic copolymer, functionalized styrenic terpolymer, styrenicterpolymer, cellulose polymer, liquid crystal polymer, ethylene-vinylacetate copolymers, polyurea, and polysiloxane or anymetallocene-catalyzed polymers of these species.

Suitable polyamides for use as an additional polymeric material incompositions within the scope of the present invention also includeresins obtained by: (1) polycondensation of (a) a dicarboxylic acid,such as oxalic acid, adipic acid, sebacic acid, terephthalic acid,isophthalic acid, or 1,4-cyclohexanedicarboxylic acid, with (b) adiamine, such as ethylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, or decamethylenediamine,1,4-cyclohexanediamine, or m-xylylenediamine; (2) a ring-openingpolymerization of cyclic lactam, such as ε-caprolactam or Ω-laurolactam;(3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproicacid, 9-aminononanoic acid, 11-aminoundecanoic acid, or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine. Specific examples of suitablepolyamides include NYLON 6, NYLON 66, NYLON 610, NYLON 11, NYLON 12,copolymerized NYLON, NYLON MXD6, and NYLON 46.

Suitable peroxide initiating agents include dicumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy) hexane;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne;2,5-dimethyl-2,5-di(benzoylperoxy)hexane;2,2′-bis(t-butylperoxy)-di-iso-propylbenzene;1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane; n-butyl4,4-bis(t-butyl-peroxy)valerate; t-butyl perbenzoate; benzoyl peroxide;n-butyl 4,4′-bis(butylperoxy) valerate; di-t-butyl peroxide; or2,5-di-(t-butylperoxy)-2,5-dimethyl hexane, lauryl peroxide, t-butylhydroperoxide, α-α bis(t-butylperoxy) diisopropylbenzene,di(2-t-butyl-peroxyisopropyl)benzene, di-t-amyl peroxide, di-t-butylperoxide. Preferably, the rubber composition includes from about 0.25 toabout 5.0 parts by weight peroxide per 100 parts by weight rubber (phr),more preferably 0.5 phr to 3 phr, most preferably 0.5 phr to 1.5 phr. Ina most preferred embodiment, the peroxide is present in an amount ofabout 0.8 phr. These ranges of peroxide are given assuming the peroxideis 100% active, without accounting for any carrier that might bepresent. Because many commercially available peroxides are sold alongwith a carrier compound, the actual amount of active peroxide presentmust be calculated. Commercially-available peroxide initiating agentsinclude DICUP™ family of dicumyl peroxides (including DICUP™ R, DICUP™40C and DICUP™ 40 KE) available from ARKEMA. Similar initiating agentsare available from AkroChem, Lanxess, Flexsys/Harwick and R.T.Vanderbilt. Another commercially-available and preferred initiatingagent is TRIGONOX™ 265-50B from Akzo Nobel, which is a mixture of1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane anddi(2-t-butylperoxyisopropyl) benzene. TRIGONOX™ peroxides are generallysold on a carrier compound.

Suitable reactive co-agents include, but are not limited to, metal saltsof diacrylates, dimethacrylates, and monomethacrylates suitable for usein this invention include those wherein the metal is zinc, magnesium,calcium, barium, tin, aluminum, lithium, sodium, potassium, iron,zirconium, and bismuth. Zinc diacrylate (ZDA) is preferred, but thepresent invention is not limited thereto. ZDA provides golf balls with ahigh initial velocity. The ZDA can be of various grades of purity. Forthe purposes of this invention, the lower the quantity of zinc stearatepresent in the ZDA the higher the ZDA purity. ZDA containing less thanabout 10% zinc stearate is preferable. More preferable is ZDA containingabout 4-8% zinc stearate. Suitable, commercially available zincdiacrylates include those from Cray Valley. The preferred concentrationsof ZDA that can be used are about 10 phr to about 40 phr, morepreferably 20 phr to about 35 phr, most preferably 25 phr to about 35phr. In a particularly preferred embodiment, the reactive co-agent ispresent in an amount of about 29 phr to about 31 phr.

Additional preferred co-agents that may be used alone or in combinationwith those mentioned above include, but are not limited to,trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, andthe like. It is understood by those skilled in the art, that in the casewhere these co-agents may be liquids at room temperature, it may beadvantageous to disperse these compounds on a suitable carrier topromote ease of incorporation in the rubber mixture.

Antioxidants are compounds that inhibit or prevent the oxidativebreakdown of elastomers, and/or inhibit or prevent reactions that arepromoted by oxygen radicals. Some exemplary antioxidants that may beused in the present invention include, but are not limited to, quinolinetype antioxidants, amine type antioxidants, and phenolic typeantioxidants. A preferred antioxidant is2,2′-methylene-bis-(4-methyl-6-t-butylphenol) available as VANOX® MBPCfrom R.T. Vanderbilt. Other polyphenolic antioxidants include VANOX® T,VANOX® L, VANOX® SKT, VANOX® SWP, VANOX® 13 and VANOX® 1290.

Suitable antioxidants include, but are not limited to,alkylene-bis-alkyl substituted cresols, such as4,4′-methylene-bis(2,5-xylenol); 4,4′-ethylidene-bis-(6-ethyl-m-cresol);4,4′-butylidene-bis-(6-t-butyl-m-cresol);4,4′-decylidene-bis-(6-methyl-m-cresol);4,4′-methylene-bis-(2-amyl-m-cresol);4,4′-propylidene-bis-(5-hexyl-m-cresol);3,3′-decylidene-bis-(5-ethyl-p-cresol);2,2′-butylidene-bis-(3-n-hexyl-p-cresol);4,4′-(2-butylidene)-bis-(6-t-butyl-m-cresol);3,3′-4(decylidene)-bis-(5-ethyl-p-cresol);(2,5-dimethyl-4-hydroxyphenyl) (2-hydroxy-3,5-dimethylphenyl) methane;(2-methyl-4-hydroxy-5-ethylphenyl) (2-ethyl-3-hydroxy-5-methylphenyl)methane; (3-methyl-5-hydroxy-6-t-butylphenyl)(2-hydroxy-4-methyl-5-decylphenyl)-n-butyl methane;(2-hydroxy-4-ethyl-5-methylphenyl)(2-decyl-3-hydroxy-4-methylphenyl)butylamylmethane;(3-ethyl-4-methyl-5-hydroxyphenyl)-(2,3-dimethyl-3-hydroxy-phenyl)nonylmethane;(3-methyl-2-hydroxy-6-ethylphenyl)-(2-isopropyl-3-hydroxy-5-methyl-phenyl)cyclohexylmethane;(2-methyl-4-hydroxy-5-methylphenyl)(2-hydroxy-3-methyl-5-ethylphenyl)dicyclohexyl methane; and the like.

Other suitable antioxidants include, but are not limited to, substitutedphenols, such as 2-tert-butyl-4-methoxyphenol;3-tert-butyl-4-methoxyphenol; 3-tert-octyl-4-methoxyphenol;2-methyl-4-methoxyphenol; 2-stearyl-4-n-butoxyphenol;3-t-butyl-4-stearyloxyphenol; 3-lauryl-4-ethoxyphenol;2,5-di-t-butyl-4-methoxyphenol; 2-methyl-4-methoxyphenol;2-(1-methycyclohexyl)-4-methoxyphenol; 2-t-butyl-4-dodecyloxyphenol;2-(1-methylbenzyl)-4-methoxyphenol; 2-t-octyl-4-methoxyphenol; methylgallate; n-propyl gallate; n-butyl gallate; lauryl gallate; myristylgallate; stearyl gallate; 2,4,5-trihydroxyacetophenone;2,4,5-trihydroxy-n-butyrophenone; 2,4,5-trihydroxystearophenone;2,6-ditert-butyl-4-methylphenol; 2,6-ditert-octyl-4-methylphenol;2,6-ditert-butyl-4-stearylphenol; 2-methyl-4-methyl-6-tert-butylphenol;2,6-distearyl-4-methylphenol; 2,6-dilauryl-4-methylphenol;2,6-di(n-octyl)-4-methylphenol; 2,6-di(n-hexadecyl)-4-methylphenol;2,6-di(1-methylundecyl)-4-methylphenol;2,6-di(1-methylheptadecyl)-4-methylphenol;2,6-di(trimethylhexyl)-4-methylphenol;2,6-di(1,1,3,3-tetramethyloctyl)-4-methylphenol; 2-n-dodecyl-6-tertbutyl-4-methylphenol; 2-n-dodecyl-6-(1-methylundecyl)-4-methylphenol;2-n-dodecyl-6-(1,1,3,3-tetramethyloctyl)-4-methylphenol;2-n-dodecyl-6-n-octadecyl-4-methylphenol;2-n-dodecyl-6-n-octyl-4-methylphenol;2-methyl-6-n-octadecyl-4-methylphenol;2-n-dodecyl-6-(1-methylheptadecyl)-4-methylphenol;2,6-di(1-methylbenzyl)-4-methylphenol;2,6-di(1-methylcyclohexyl)-4-methylphenol;2,6-(1-methylcyclohexyl)-4-methylphenol;2-(1-methylbenzyl)-4-methylphenol; and related substituted phenols.

More suitable antioxidants include, but are not limited to, alkylenebisphenols, such as 4,4′-butylidene bis(3-methyl-6-t-butyl phenol);2,2-butylidene bis (4,6-dimethyl phenol); 2,2′-butylidenebis(4-methyl-6-t-butyl phenol); 2,2′-butylidene bis(4-t-butyl-6-methylphenol); 2,2′-ethylidene bis(4-methyl-6-t-butylphenol); 2,2′-methylenebis(4,6-dimethyl phenol); 2,2′-methylene bis(4-methyl-6-t-butyl phenol);2,2′-methylene bis(4-ethyl-6-t-butyl phenol); 4,4′-methylenebis(2,6-di-t-butyl phenol); 4,4′-methylene bis(2-methyl-6-t-butylphenol); 4,4′-methylene bis(2,6-dimethyl phenol); 2,2′-methylenebis(4-t-butyl-6-phenyl phenol);2,2′-dihydroxy-3,3′,5,5′-tetramethylstilbene; 2,2′-isopropylidenebis(4-methyl-6-t-butyl phenol); ethylene bis (beta-naphthol);1,5-dihydroxy naphthalene; 2,2′-ethylene bis (4-methyl-6-propyl phenol);4,4′-methylene bis(2-propyl-6-t-butyl phenol); 4,4′-ethylene bis(2-methyl-6-propyl phenol); 2,2′-methylene bis(5-methyl-6-t-butylphenol); and 4,4′-butylidene bis(6-t-butyl-3-methyl phenol);

Suitable antioxidants further include, but are not limited to, alkylenetrisphenols, such as 2,6-bis (2′-hydroxy-3′-t-butyl-5′-methylbenzyl)-4-methyl phenol; 2,6-bis (2′-hydroxy-3′-t-ethyl-5′-butylbenzyl)-4-methyl phenol; and 2,6-bis(2′-hydroxy-3′-t-butyl-5′-propylbenzyl)-4-methyl phenol.

The antioxidant is typically present in an amount of about 0.1 phr toabout 5 phr, preferably from about 0.1 phr to about 2 phr, morepreferably about 0.1 phr to about 1 phr. In a particularly preferredembodiment, the antioxidant is present in an amount of about 0.4 phr. Inan alternative embodiment, the antioxidant should be present in anamount to ensure that the hardness gradient of the inventive cores isnegative. Preferably, about 0.2 phr to about 1 phr antioxidant is addedto the core layer (inner core or outer core layer) formulation, morepreferably, about 0.3 to about 0.8 phr, and most preferably 0.4 to about0.7 phr. Preferably, about 0.25 phr to about 1.5 phr of peroxide ascalculated at 100% active can be added to the core formulation, morepreferably about 0.5 phr to about 1.2 phr, and most preferably about 0.7phr to about 1.0 phr. The ZDA amount can be varied to suit the desiredcompression, spin and feel of the resulting golf ball. The cure regimecan have a temperature range between from about 290° F. to about 360°F., or from about 290° F. to about 335° F., or from about 300° F. toabout 325° F., or from about 330° F. to about 355° F., and the stock isheld at that temperature for at least about 10 minutes to about 30minutes.

The thermoset rubber composition in a core of the golf ball of thepresent invention may also include an optional soft and fast agent. Asused herein, “soft and fast agent” means any compound or a blend thereofthat that is capable of making a core 1) be softer (lower compression)at constant COR or 2) have a higher COR at equal compression, or anycombination thereof, when compared to a core equivalently preparedwithout a soft and fast agent. Preferably, the composition of thepresent invention contains from about 0.05 phr to about 10.0 phr softand fast agent. In one embodiment, the soft and fast agent is present inan amount of about 0.05 phr to about 3.0 phr, preferably about 0.05 phrto about 2.0 phr, more preferably about 0.05 phr to about 1.0 phr. Inanother embodiment, the soft and fast agent is present in an amount ofabout 2.0 phr to about 5.0 phr, preferably about 2.35 phr to about 4.0phr, and more preferably about 2.35 phr to about 3.0 phr. In analternative high concentration embodiment, the soft and fast agent ispresent in an amount of about 5.0 phr to about 10.0 phr, more preferablyabout 6.0 phr to about 9.0 phr, most preferably about 7.0 phr to about8.0 phr. In a most preferred embodiment, the soft and fast agent ispresent in an amount of about 2.6 phr.

Suitable soft and fast agents include, but are not limited to,organosulfur or metal-containing organosulfur compounds, an organicsulfur compound, including mono, di, and polysulfides, a thiol, ormercapto compound, an inorganic sulfide compound, a Group VIA compound,or mixtures thereof. The soft and fast agent component may also be ablend of an organosulfur compound and an inorganic sulfide compound.

Suitable soft and fast agents of the present invention include, but arenot limited to those having the following general formula:

where R₁-R₅ can be C₁-C₈ alkyl groups; halogen groups; thiol groups(—SH), carboxylated groups; sulfonated groups; and hydrogen; in anyorder; and also pentafluorothiophenol; 2-fluorothiophenol;3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol;2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol;2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol;4-chlorotetrafluorothiophenol; pentachlorothiophenol;2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol;2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol;3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol;2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol;pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol;4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol;3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol;3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol;2,3,5,6-tetrabromothiophenol; pentaiodothiophenol; 2-iodothiophenol;3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol;2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol;2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenoland; and their zinc salts. Preferably, thehalogenated thiophenol compound is pentachlorothiophenol, which iscommercially available in neat form or under the tradename STRUKTOL®, aclay-based carrier containing the sulfur compound pentachlorothiophenolloaded at 45 percent (correlating to 2.4 parts PCTP). STRUKTOL® iscommercially available from Struktol Company of America of Stow, Ohio.PCTP is commercially available in neat form from eChinachem of SanFrancisco, Calif. and in the salt form from eChinachem of San Francisco,Calif. Most preferably, the halogenated thiophenol compound is the zincsalt of pentachlorothiophenol, which is commercially available fromeChinachem of San Francisco, Calif.

As used herein when referring to the invention, the term “organosulfurcompound(s)” refers to any compound containing carbon, hydrogen, andsulfur, where the sulfur is directly bonded to at least 1 carbon. Asused herein, the term “sulfur compound” means a compound that iselemental sulfur, polymeric sulfur, or a combination thereof. It shouldbe further understood that the term “elemental sulfur” refers to thering structure of S₈ and that “polymeric sulfur” is a structureincluding at least one additional sulfur relative to elemental sulfur.

Additional suitable examples of soft and fast agents (that are alsobelieved to be cis-to-trans catalysts) include, but are not limited to,4,4′-diphenyl disulfide; 4,4′-ditolyl disulfide; 2,2′-benzamido diphenyldisulfide; bis(2-aminophenyl) disulfide; bis(4-aminophenyl) disulfide;bis(3-aminophenyl) disulfide; 2,2′-bis(4-aminonaphthyl) disulfide;2,2′-bis(3-aminonaphthyl) disulfide; 2,2′-bis(4-aminonaphthyl)disulfide; 2,2′-bis(5-aminonaphthyl) disulfide;2,2′-bis(6-aminonaphthyl) disulfide; 2,2′-bis(7-aminonaphthyl)disulfide; 2,2′-bis(8-aminonaphthyl) disulfide;1,1′-bis(2-aminonaphthyl) disulfide; 1,1′-bis(3-aminonaphthyl)disulfide; 1,1′-bis(3-aminonaphthyl) disulfide;1,1′-bis(4-aminonaphthyl) disulfide; 1,1′-bis(5-aminonaphthyl)disulfide; 1,1′-bis(6-aminonaphthyl) disulfide;1,1′-bis(7-aminonaphthyl) disulfide; 1,1′-bis(8-aminonaphthyl)disulfide; 1,2′-diamino-1,2′-dithiodinaphthalene;2,3′-diamino-1,2′-dithiodinaphthalene; bis(4-chlorophenyl) disulfide;bis(2-chlorophenyl) disulfide; bis(3-chlorophenyl) disulfide;bis(4-bromophenyl) disulfide; bis(2-bromophenyl) disulfide;bis(3-bromophenyl) disulfide; bis(4-fluorophenyl) disulfide;bis(4-iodophenyl) disulfide; bis(2,5-dichlorophenyl) disulfide;bis(3,5-dichlorophenyl) disulfide; bis (2,4-dichlorophenyl) disulfide;bis(2,6-dichlorophenyl) disulfide; bis(2,5-dibromophenyl) disulfide;bis(3,5-dibromophenyl) disulfide; bis(2-chloro-5-bromophenyl) disulfide;bis(2,4,6-trichlorophenyl) disulfide; bis(2,3,4,5,6-pentachlorophenyl)disulfide; bis(4-cyanophenyl) disulfide; bis(2-cyanophenyl) disulfide;bis(4-nitrophenyl) disulfide; bis(2-nitrophenyl) disulfide;2,2′-dithiobenzoic acid ethylester; 2,2′-dithiobenzoic acid methylester;2,2′-dithiobenzoic acid; 4,4′-dithiobenzoic acid ethylester;bis(4-acetylphenyl) disulfide; bis(2-acetylphenyl) disulfide;bis(4-formylphenyl) disulfide; bis(4-carbamoylphenyl) disulfide;1,1′-dinaphthyl disulfide; 2,2′-dinaphthyl disulfide; 1,2′-dinaphthyldisulfide; 2,2′-bis(1-chlorodinaphthyl) disulfide;2,2′-bis(1-bromonaphthyl) disulfide; 1,1′-bis(2-chloronaphthyl)disulfide; 2,2′-bis(1-cyanonaphthyl) disulfide;2,2′-bis(1-acetylnaphthyl) disulfide; and the like; or a mixturethereof. Preferred organosulfur components include 4,4′-diphenyldisulfide, 4,4′-ditolyl disulfide, or 2,2′-benzamido diphenyl disulfide,or a mixture thereof. A more preferred organosulfur component includes4,4′-ditolyl disulfide. In another embodiment, metal-containingorganosulfur components can be used according to the invention. Suitablemetal-containing organosulfur components include, but are not limitedto, cadmium, copper, lead, and tellurium analogs ofdiethyldithiocarbamate, diamyldithiocarbamate, anddimethyldithiocarbamate, or mixtures thereof.

Suitable substituted or unsubstituted aromatic organic components thatdo not include sulfur or a metal include, but are not limited to,4,4′-diphenyl acetylene, azobenzene, or a mixture thereof. The aromaticorganic group preferably ranges in size from C₆ to C₂₀, and morepreferably from C₆ to C₁₀. Suitable inorganic sulfide componentsinclude, but are not limited to titanium sulfide, manganese sulfide, andsulfide analogs of iron, calcium, cobalt, molybdenum, tungsten, copper,selenium, yttrium, zinc, tin, and bismuth.

A substituted or unsubstituted aromatic organic compound is alsosuitable as a soft and fast agent. Suitable substituted or unsubstitutedaromatic organic components include, but are not limited to, componentshaving the formula (R₁)_(x)—R₃-M-R₄—(R₂)_(y), wherein R₁ and R₂ are eachhydrogen or a substituted or unsubstituted C₁₋₂₀ linear, branched, orcyclic alkyl, alkoxy, or alkylthio group, or a single, multiple, orfused ring C₆ to C₂₄ aromatic group; x and y are each an integer from 0to 5; R₃ and R₄ are each selected from a single, multiple, or fused ringC₆ to C₂₄ aromatic group; and M includes an azo group or a metalcomponent. R₃ and R₄ are each preferably selected from a C₆ to C₁₀aromatic group, more preferably selected from phenyl, benzyl, naphthyl,benzamido, and benzothiazyl. R₁ and R₂ are each preferably selected froma substituted or unsubstituted C₁₋₁₀ linear, branched, or cyclic alkyl,alkoxy, or alkylthio group or a C₆ to C₁₀ aromatic group. When R₁, R₂,R₃, or R₄, are substituted, the substitution may include one or more ofthe following substituent groups: hydroxy and metal salts thereof;mercapto and metal salts thereof; halogen; amino, nitro, cyano, andamido; carboxyl including esters, acids, and metal salts thereof; silyl;acrylates and metal salts thereof; sulfonyl or sulfonamide; andphosphates and phosphites. When M is a metal component, it may be anysuitable elemental metal available to those of ordinary skill in theart. Typically, the metal will be a transition metal, althoughpreferably it is tellurium or selenium. In one embodiment, the aromaticorganic compound is substantially free of metal, while in anotherembodiment the aromatic organic compound is completely free of metal.

The soft and fast agent can also include a Group VIA component.Elemental sulfur and polymeric sulfur are commercially available fromElastochem, Inc. of Chardon, Ohio Exemplary sulfur catalyst compoundsinclude PB(RM-S)-80 elemental sulfur and PB(CRST)-65 polymeric sulfur,each of which is available from Elastochem, Inc. An exemplary telluriumcatalyst under the tradename TELLOY® and an exemplary selenium catalystunder the tradename VANDEX® are each commercially available from RTVanderbilt.

Fillers may also be added to the thermoset rubber composition of thecore to adjust the density of the composition, up or down. Typically,fillers include materials such as tungsten, zinc oxide, barium sulfate,silica, calcium carbonate, zinc carbonate, metals, metal oxides andsalts, regrind (recycled core material typically ground to about 30 meshparticle), high-Mooney-viscosity rubber regrind, trans-regrind corematerial (recycled core material containing high trans-isomer ofpolybutadiene), and the like. When trans-regrind is present, the amountof trans-isomer is preferably between about 10% and about 60%. In apreferred embodiment of the invention, the core comprises polybutadienehaving a cis-isomer content of greater than about 95% and trans-regrindcore material (already vulcanized) as a filler. Any particle sizetrans-regrind core material is sufficient, but is preferably less thanabout 125 μm.

Fillers added to one or more portions of the golf ball typically includeprocessing aids or compounds to affect rheological and mixingproperties, density-modifying fillers, tear strength, or reinforcementfillers, and the like. The fillers are generally inorganic, and suitablefillers include numerous metals or metal oxides, such as zinc oxide andtin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate,barium carbonate, clay, tungsten, tungsten carbide, an array of silicas,and mixtures thereof. Fillers may also include various foaming agents orblowing agents which may be readily selected by one of ordinary skill inthe art. Fillers may include polymeric, ceramic, metal, and glassmicrospheres may be solid or hollow, and filled or unfilled. Fillers aretypically also added to one or more portions of the golf ball to modifythe density thereof to conform to uniform golf ball standards. Fillersmay also be used to modify the weight of the center or at least oneadditional layer for specialty balls, e.g., a lower weight ball ispreferred for a player having a low swing speed.

Materials such as tungsten, zinc oxide, barium sulfate, silica, calciumcarbonate, zinc carbonate, metals, metal oxides and salts, and regrind(recycled core material typically ground to about 30 mesh particle) arealso suitable fillers.

The polybutadiene and/or any other base rubber or elastomer system mayalso be foamed, or filled with hollow microspheres or with expandablemicrospheres which expand at a set temperature during the curing processto any low specific gravity level. Other ingredients such as sulfuraccelerators, e.g., tetramethylthiuram di, tri, or tetrasulfide, and/ormetal-containing organosulfur components may also be used according tothe invention. Suitable metal-containing organosulfur acceleratorsinclude, but are not limited to, cadmium, copper, lead, and telluriumanalogs of diethyldithiocarbamate, diamyldithiocarbamate, anddimethyldithiocarbamate, or mixtures thereof. Other ingredients such asprocessing aids e.g., fatty acids and/or their metal salts, processingoils, dyes and pigments, as well as other additives known to one skilledin the art may also be used in the present invention in amountssufficient to achieve the purpose for which they are typically used.

Without being bound by theory, it is believed that the percentage ofdouble bonds in the trans configuration may be manipulated throughout acore containing at least one main-chain unsaturated rubber (i.e.,polybutadiene), plastic, or elastomer resulting in a trans gradient. Thetrans gradient may be influenced (up or down) by changing the type andamount of cis-to-trans catalyst (or soft-and-fast agent), the type andamount of peroxide, and the type and amount of coagent in theformulation. For example, a formulation containing about 0.25 phr ZnPCTPmay have a trans gradient of about 5% across the core whereas aformulation containing about 2 phr ZnPCTP may have a trans gradient ofabout 10%, or higher. The trans gradient may also be manipulated throughthe cure times and temperatures. It is believed that lower temperaturesand shorter cure times yield lower trans gradients, although acombination of many of these factors may yield gradients of differingand/or opposite directions from that resulting from use of a singlefactor.

In general, higher and/or faster cure rates tend to yield higher levelsof trans content, as do higher concentrations of peroxides,soft-and-fast agents, and, to some extent, ZDA concentration. Even thetype of rubber may have an effect on trans levels, with those catalyzedby rare-earth metals, such as Nd, being able to form higher levels oftrans polybutadiene compared to those rubbers formed from Group VIIImetals, such as Co, Ni, and Li.

The optional intermediate layer(s) are not limited by a particularcomposition for forming the layer(s), and can be formed from anysuitable golf ball composition including, but not limited to, naturalrubber; polybutadiene; polyisoprene; ethylene propylene rubber;ethylene-propylene-diene rubber; styrene-butadiene rubber; butyl rubber;halobutyl rubber; thermoset polyurethane; thermoset polyurea;acrylonitrile butadiene rubber; polychloroprene; alkyl acrylate rubber;chlorinated isoprene rubber; acrylonitrile chlorinated isoprene rubber;polyalkenamer rubber; polyester; polyacrylate; partially- andfully-neutralized ionomer; graft copolymer of ionomer and polyamide;polyester, particularly polyesters modified with a compatibilizing groupsuch as sulfonate or phosphonate, including modified poly(ethyleneterephthalate), modified poly(butylene terephthalate), modifiedpoly(propylene terephthalate), modified poly(trimethyleneterephthalate), modified poly(ethylene naphthenate), including, but notlimited to, those disclosed in U.S. Pat. Nos. 6,353,050, 6,274,298, and6,001,930, the entire disclosures of which are hereby incorporatedherein by reference; polyamides, polyamide-ethers, and polyamide-esters,including, but not limited to, those disclosed in U.S. Pat. Nos.6,187,864, 6,001,930, and 5,981,654, the entire disclosures of which arehereby incorporated herein by reference; polyurethanes, polyureas, andpolyurethane-polyurea hybrids, including, but not limited to, thosedisclosed in U.S. Pat. Nos. 5,334,673, 5,484,870, 6,506,851, 6,756,436,6,835,794, 6,867,279, 6,960,630, and 7,105,623, U.S. Patent ApplicationPublication No. 2007/0117923, and U.S. Patent Application Ser. Nos.60/401,047 and Ser. No. 13/613,095, the entire disclosures of which arehereby incorporated herein by reference; fluoropolymers, including, butnot limited to, those disclosed in U.S. Pat. Nos. 5,691,066, 6,747,110and 7,009,002, the entire disclosures of which are hereby incorporatedherein by reference; non-ionomeric acid polymers, i.e., E/X- andE/X/Y-type copolymers, including, but not limited to, those disclosed inU.S. Pat. No. 6,872,774, the entire disclosure of which is herebyincorporated herein by reference; metallocene-catalyzed polymers,including, but not limited to, those disclosed in U.S. Pat. Nos.6,274,669, 5,919,862, 5,981,654, and 5,703,166, the entire disclosuresof which are hereby incorporated herein by reference; polystyrenes, suchas poly(styrene-co-maleic anhydride), acrylonitrile-butadiene-styrene,poly(styrene sulfonate), polyethylene styrene; polypropylenes,polyethylenes, propylene elastomers, ethylene elastomers, and copolymersof propylene and ethylene; polyvinyl chlorides; polyvinyl acetates,preferably having less than about 9% of vinyl acetate by weight;polycarbonates, blends of polycarbonate/acrylonitrile-butadiene-styrene,blends of polycarbonate/polyurethane, and blends ofpolycarbonate/polyester; polyvinyl alcohols; polyethers, such aspolyarylene ethers, polyphenylene oxides, and block copolymers ofalkenyl aromatics with vinyl aromatics and poly(amic ester)s;polyimides, polyetherketones, and polyamideimides;polycarbonate/polyester copolymers; and combinations of two or morethereof.

Thermoplastic core compositions are optionally treated or admixed with athermoset diene composition to reduce or prevent flow upon overmolding.Optional treatments may also include the addition of peroxide to thematerial prior to molding, or a post-molding treatment with, forexample, a crosslinking solution, electron beam, gamma radiation,isocyanate or amine solution treatment, or the like. Such treatments mayprevent the intermediate layer from melting and flowing or “leaking” outat the mold equator, as thermoset layers are molded thereon at atemperature necessary to crosslink the thermoset layer, which istypically from 280° F. to 360° F. for a period of about 5 to 30 minutes.

The multi-layer core is enclosed with a cover, which may be a single-,dual-, or multi-layer cover, preferably having an overall thicknesswithin a range having a lower limit of 0.010 or 0.020 or 0.025 or 0.030or 0.040 or 0.045 inches and an upper limit of 0.050 or 0.060 or 0.070or 0.075 or 0.080 or 0.090 or 0.100 or 0.150 or 0.200 or 0.300 or 0.500inches. In a particular embodiment, the cover is a single layer having athickness of from 0.010 or 0.020 or 0.025 inches to 0.035 or 0.040 or0.050 inches. In another particular embodiment, the cover consists of aninner cover layer having a thickness of from 0.010 or 0.020 or 0.025inches to 0.035 or 0.050 inches and an outer cover layer having athickness of from 0.010 or 0.020 or 0.025 inches to 0.035 or 0.040inches.

Suitable cover materials include, but are not limited to, polyurethanes,polyureas, and hybrids of polyurethane and polyurea; ionomer resins andblends thereof (e.g., Surlyn® ionomer resins and DuPont® HPF 1000 andHPF 2000, commercially available from E. I. du Pont de Nemours andCompany; Iotek® ionomers, commercially available from ExxonMobilChemical Company; Amplify® IO ionomers of ethylene acrylic acidcopolymers, commercially available from The Dow Chemical Company; andClarix® ionomer resins, commercially available from A. Schulman Inc.);polyisoprene; polyoctenamer, such as Vestenamer® polyoctenamer,commercially available from Evonik Industries; polyethylene, including,for example, low density polyethylene, linear low density polyethylene,and high density polyethylene; polypropylene; rubber-toughened olefinpolymers; non-ionomeric acid copolymers, e.g., (meth)acrylic acid, whichdo not become part of an ionomeric copolymer; plastomers; flexomers;styrene/butadiene/styrene block copolymers;styrene/ethylene-butylene/styrene block copolymers; polybutadiene;styrene butadiene rubber; ethylene propylene rubber; ethylene propylenediene rubber; dynamically vulcanized elastomers; ethylene vinylacetates; ethylene (meth) acrylates; polyvinyl chloride resins;polyamides, amide-ester elastomers, and copolymers of ionomer andpolyamide, including, for example, Pebax® thermoplastic polyether andpolyester amides, commercially available from Arkema Inc; crosslinkedtrans-polyisoprene; polyester-based thermoplastic elastomers, such asHytrel® polyester elastomers, commercially available from E. I. du Pontde Nemours and Company, and Riteflex® polyester elastomers, commerciallyavailable from Ticona; polyurethane-based thermoplastic elastomers, suchas Elastollan® polyurethanes, commercially available from BASF;synthetic or natural vulcanized rubber; and combinations thereof.

Compositions comprising an ionomer or a blend of two or more ionomersare particularly suitable cover materials. Preferred ionomeric covercompositions include:

-   -   (a) a composition comprising a “high acid ionomer” (i.e., having        an acid content of greater than 16 wt %), such as Surlyn 8150®;    -   (b) a composition comprising a high acid ionomer and a maleic        anhydride-grafted non-ionomeric polymer (e.g., Fusabond®        functionalized polymers). A particularly preferred blend of high        acid ionomer and maleic anhydride-grafted polymer is a 84 wt        %/16 wt % blend of Surlyn 8150® and Fusabond®. Blends of high        acid ionomers with maleic anhydride-grafted polymers are further        disclosed, for example, in U.S. Pat. Nos. 6,992,135 and        6,677,401, the entire disclosures of which are hereby        incorporated herein by reference;    -   (c) a composition comprising a 50/45/5 blend of Surlyn®        8940/Surlyn® 9650/Nucrel® 960, preferably having a material        hardness of from 80 to 85 Shore C;    -   (d) a composition comprising a 50/25/25 blend of Surlyn®        8940/Surlyn® 9650/Surlyn® 9910, preferably having a material        hardness of about 90 Shore C;    -   (e) a composition comprising a 50/50 blend of Surlyn®        8940/Surlyn® 9650, preferably having a material hardness of        about 86 Shore C;    -   (f) a composition comprising a blend of Surlyn® 7940/Surlyn®        8940, optionally including a melt flow modifier;    -   (g) a composition comprising a blend of a first high acid        ionomer and a second high acid ionomer, wherein the first high        acid ionomer is neutralized with a different cation than the        second high acid ionomer (e.g., 50/50 blend of Surlyn® 8150 and        Surlyn® 9150), optionally including one or more melt flow        modifiers such as an ionomer, ethylene-acid copolymer or ester        terpolymer; and    -   (h) a composition comprising a blend of a first high acid        ionomer and a second high acid ionomer, wherein the first high        acid ionomer is neutralized with a different cation than the        second high acid ionomer, and from 0 to 10 wt % of an        ethylene/acid/ester ionomer wherein the ethylene/acid/ester        ionomer is neutralized with the same cation as either the first        high acid ionomer or the second high acid ionomer or a different        cation than the first and second high acid ionomers (e.g., a        blend of 40-50 wt % Surlyn® 8140, 40-50 wt % Surlyn® 9120, and        0-10 wt % Surlyn® 6320).

Surlyn 8150®, Surlyn® 8940, and Surlyn® 8140 are different grades ofE/MAA copolymer in which the acid groups have been partially neutralizedwith sodium ions. Surlyn® 9650, Surlyn® 9910, Surlyn® 9150, and Surlyn®9120 are different grades of E/MAA copolymer in which the acid groupshave been partially neutralized with zinc ions. Surlyn® 7940 is an E/MAAcopolymer in which the acid groups have been partially neutralized withlithium ions. Surlyn® 6320 is a very low modulus magnesium ionomer witha medium acid content. Nucrel® 960 is an E/MAA copolymer resin nominallymade with 15 wt % methacrylic acid. Surlyn® ionomers, Fusabond®polymers, and Nucrel® copolymers are commercially available from E. I.du Pont de Nemours and Company.

Ionomeric cover compositions can be blended with non-ionic thermoplasticresins, particularly to manipulate product properties. Examples ofsuitable non-ionic thermoplastic resins include, but are not limited to,polyurethane, poly-ether-ester, poly-amide-ether, polyether-urea,thermoplastic polyether block amides (e.g., Pebax® block copolymers,commercially available from Arkema Inc.), styrene-butadiene-styreneblock copolymers, styrene(ethylene-butylene)-styrene block copolymers,polyamides, polyesters, polyolefins (e.g., polyethylene, polypropylene,ethylene-propylene copolymers, polyethylene-(meth)acrylate,plyethylene-(meth)acrylic acid, functionalized polymers with maleicanhydride grafting, Fusabond® functionalized polymers commerciallyavailable from E. I. du Pont de Nemours and Company, functionalizedpolymers with epoxidation, elastomers (e.g., ethylene propylene dienemonomer rubber, metallocene-catalyzed polyolefin) and ground powders ofthermoset elastomers.

Ionomer golf ball cover compositions may include a flow modifier, suchas, but not limited to, acid copolymer resins (e.g., Nucrel® acidcopolymer resins, and particularly Nucrel® 960, commercially availablefrom E. I. du Pont de Nemours and Company), performance additives (e.g.,A-C® performance additives, particularly A-C® low molecular weightionomers and copolymers, A-C® oxidized polyethylenes, and A-C® ethylenevinyl acetate waxes, commercially available from Honeywell InternationalInc.), fatty acid amides (e.g., ethylene bis-stearamide and ethylenebis-oleamide), fatty acids and salts thereof

Suitable ionomeric cover materials are further disclosed, for example,in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,894,098, 6,919,393, and6,953,820, the entire disclosures of which are hereby incorporated byreference.

Polyurethanes, polyureas, and blends and hybrids ofpolyurethane/polyurea are also particularly suitable for forming coverlayers. Suitable polyurethanes and polyureas are further disclosed, forexample, in U.S. Pat. Nos. 5,334,673, 5,484,870, 6,506,851, 6,756,436,6,835,794, 6,867,279, 6,960,630, and 7,105,623; U.S. Patent ApplicationPublication No. 2009/0011868; and U.S. Patent Application No.60/401,047, the entire disclosures of which are hereby incorporatedherein by reference. Suitable polyurethane-urea cover materials includepolyurethane/polyurea blends and copolymers comprising urethane and ureasegments, as disclosed in U.S. Patent Application Publication No.2007/0117923, the entire disclosure of which is hereby incorporatedherein by reference.

Cover compositions may include one or more filler(s), such as titaniumdioxide, barium sulfate, etc., and/or additive(s), such as coloringagents, fluorescent agents, whitening agents, antioxidants, dispersants,UV absorbers, light stabilizers, plasticizers, surfactants,compatibility agents, foaming agents, reinforcing agents, releaseagents, and the like.

Suitable cover materials and constructions also include, but are notlimited to, those disclosed in U.S. Patent Application Publication No.2005/0164810, U.S. Pat. Nos. 5,919,100, 6,117,025, 6,767,940, and6,960,630, and PCT Publications WO00/23519 and WO00/29129, the entiredisclosures of which are hereby incorporated herein by reference.

In a particular embodiment, the cover is a single layer, preferablyformed from an ionomeric composition having a material hardness of 60Shore D or greater or a material hardness of from 60 or 62 or 65 Shore Dto 65 or 70 or 72 Shore D, and a thickness of 0.02 inches or greater or0.03 inches or greater or 0.04 inches or greater or a thickness within arange having a lower limit of 0.010 or 0.015 or 0.020 inches and anupper limit of 0.035 or 0.040 or 0.050 inches.

In another particular embodiment, the cover is a single layer having athickness of from 0.010 or 0.025 inches to 0.035 or 0.040 inches andformed from a thermoplastic composition selected from ionomer-,polyurethane-, and polyurea-based compositions having a materialhardness of 62 Shore D or less, or less than 62 Shore D, or 60 Shore Dor less, or less than 60 Shore D, or 55 Shore D or less, or less than 55Shore D.

In another particular embodiment, the cover is a single layer having athickness of from 0.010 or 0.025 inches to 0.035 or 0.040 inches andformed from a thermosetting polyurethane- or polyurea-based compositionhaving a material hardness of 62 Shore D or less, or less than 62 ShoreD, or 60 Shore D or less, or less than 60 Shore D, or 55 Shore D orless, or less than 55 Shore D.

In another particular embodiment, the cover comprises an inner coverlayer formed from an ionomeric composition and an outer cover layerformed from a thermosetting polyurethane- or polyurea-based composition.The inner cover layer composition preferably has a material hardness offrom 60 or 62 or 65 Shore D to 65 or 70 or 72 Shore D. The inner coverlayer preferably has a thickness within a range having a lower limit of0.010 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.040 or0.050 inches. The outer cover layer composition preferably has amaterial hardness of 62 Shore D or less, or less than 62 Shore D, or 60Shore D or less, or less than 60 Shore D, or 55 Shore D or less, or lessthan 55 Shore D. The outer cover layer preferably has a thickness withina range having a lower limit of 0.010 or 0.020 or 0.025 inches and anupper limit of 0.035 or 0.040 or 0.050 inches.

In another particular embodiment, the cover comprises an inner coverlayer formed from an ionomeric composition and an outer cover layerformed from a thermoplastic composition selected from ionomer-,polyurethane-, and polyurea-based compositions. The inner cover layercomposition preferably has a material hardness of from 60 or 62 or 65Shore D to 65 or 70 or 72 Shore D. The inner cover layer preferably hasa thickness within a range having a lower limit of 0.010 or 0.020 or0.030 inches and an upper limit of 0.035 or 0.040 or 0.050 inches. Theouter cover layer composition preferably has a material hardness of 62Shore D or less, or less than 62 Shore D, or 60 Shore D or less, or lessthan 60 Shore D, or 55 Shore D or less, or less than 55 Shore D. Theouter cover layer preferably has a thickness within a range having alower limit of 0.010 or 0.020 or 0.025 inches and an upper limit of0.035 or 0.040 or 0.050 inches.

In another particular embodiment, the cover is a dual- or multi-layercover including an inner or intermediate cover layer formed from anionomeric composition and an outer cover layer formed from apolyurethane- or polyurea-based composition. The ionomeric layerpreferably has a surface hardness of 70 Shore D or less, or 65 Shore Dor less, or less than 65 Shore D, or a Shore D hardness of from 50 to65, or a Shore D hardness of from 57 to 60, or a Shore D hardness of 58,and a thickness within a range having a lower limit of 0.010 or 0.020 or0.030 inches and an upper limit of 0.045 or 0.080 or 0.120 inches. Theouter cover layer is preferably formed from a castable or reactioninjection moldable polyurethane, polyurea, or copolymer or hybrid ofpolyurethane/polyurea. Such cover material is preferably thermosetting,but may be thermoplastic. The outer cover layer composition preferablyhas a material hardness of 85 Shore C or less, or 45 Shore D or less, or40 Shore D or less, or from 25 Shore D to 40 Shore D, or from 30 Shore Dto 40 Shore D. The outer cover layer preferably has a surface hardnesswithin a range having a lower limit of 20 or 30 or 35 or 40 Shore D andan upper limit of 52 or 58 or 60 or 65 or 70 or 72 or 75 Shore D. Theouter cover layer preferably has a thickness within a range having alower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.075 or 0.080 or 0.115inches.

A moisture vapor barrier layer is optionally employed between the coreand the cover. Moisture vapor barrier layers are further disclosed, forexample, in U.S. Pat. Nos. 6,632,147, 6,838,028, 6,932,720, 7,004,854,and 7,182,702, and U.S. Patent Application Publication Nos.2003/0069082, 2003/0069085, 2003/0130062, 2004/0147344, 2004/0185963,2006/0068938, 2006/0128505 and 2007/0129172, the entire disclosures ofwhich are hereby incorporated herein by reference.

Thermoplastic layers herein may be treated in such a manner as to createa positive or negative hardness gradient. In golf ball layers of thepresent invention wherein a thermosetting rubber is used,gradient-producing processes and/or gradient-producing rubberformulation may be employed. Gradient-producing processes andformulations are disclosed more fully, for example, in U.S. patentapplication Ser. No. 12/048,665, filed on Mar. 14, 2008; Ser. No.11/829,461, filed on Jul. 27, 2007; Ser. No. 11/772,903, filed Jul. 3,2007; Ser. No. 11/832,163, filed Aug. 1, 2007; Ser. No. 11/832,197,filed on Aug. 1, 2007; the entire disclosure of each of these referencesis hereby incorporated herein by reference.

Golf balls of the present invention will typically have dimple coverageof 60% or greater, preferably 65% or greater, and more preferably 75% orgreater.

The United States Golf Association specifications limit the minimum sizeof a competition golf ball to 1.680 inches. There is no specification asto the maximum diameter, and golf balls of any size can be used forrecreational play. Golf balls of the present invention can have anoverall diameter of any size. The preferred diameter of the present golfballs is within a range having a lower limit of 1.680 inches and anupper limit of 1.740 or 1.760 or 1.780 or 1.800 inches.

Golf balls of the present invention preferably have a moment of inertia(“MOT”) of 70-95 g·cm², preferably 75-93 g·cm², and more preferably76-90 g·cm². For low MOT embodiments, the golf ball preferably has anMOT of 85 g·cm² or less, or 83 g·cm² or less. For high MOT embodiment,the golf ball preferably has an MOT of 86 g·cm² or greater, or 87 g·cm²or greater. MOI is measured on a model MOI-005-104 Moment of InertiaInstrument manufactured by Inertia Dynamics of Collinsville, Conn. Theinstrument is connected to a PC for communication via a COMM port and isdriven by MOI Instrument Software version #1.2.

For purposes of the present invention, “compression” refers to Atticompression and is measured according to a known procedure, using anAtti compression test device, wherein a piston is used to compress aball against a spring. The travel of the piston is fixed and thedeflection of the spring is measured. The measurement of the deflectionof the spring does not begin with its contact with the ball; rather,there is an offset of approximately the first 1.25 mm (0.05 inches) ofthe spring's deflection. Very low compression cores will not cause thespring to deflect by more than 1.25 mm and therefore have a zero ornegative compression measurement. The Atti compression tester isdesigned to measure objects having a diameter of 1.680 inches; thus,smaller objects, such as golf ball cores, must be shimmed to a totalheight of 1.680 inches to obtain an accurate reading. Conversion fromAtti compression to Riehle (cores), Riehle (balls), 100 kg deflection,130-10 kg deflection or effective modulus can be carried out accordingto the formulas given in Compression by Any Other Name, Science and GolfIV, Proceedings of the World Scientific Congress of Golf (Eric Thained., Routledge, 2002).

COR, as used herein, is determined according to a known procedurewherein a sphere is fired from an air cannon at two given velocities andcalculated at a velocity of 125 ft/s. Ballistic light screens arelocated between the air cannon and the steel plate at a fixed distanceto measure ball velocity. As the sphere travels toward the steel plate,it activates each light screen, and the time at each light screen ismeasured. This provides an incoming transit time period inverselyproportional to the sphere's incoming velocity. The sphere impacts thesteel plate and rebounds through the light screens, which again measuresthe time period required to transit between the light screens. Thisprovides an outgoing transit time period inversely proportional to thesphere's outgoing velocity. COR is then calculated as the ratio of theoutgoing transit time period to the incoming transit time period,COR=V_(out)/V_(in)=T_(in)/T_(out).

The surface hardness of a golf ball layer is obtained from the averageof a number of measurements taken from opposing hemispheres, taking careto avoid making measurements on the parting line of the core or onsurface defects, such as holes or protrusions. Hardness measurements aremade pursuant to ASTM D-2240 using a calibrated, digital durometer,capable of reading to 0.1 hardness units and set to record the maximumhardness reading obtained for each measurement.

The center hardness of a core is obtained according to the followingprocedure. The core is gently pressed into a hemispherical holder havingan internal diameter approximately slightly smaller than the diameter ofthe core, such that the core is held in place in the hemisphericalportion of the holder while concurrently leaving the geometric centralplane of the core exposed. The core is secured in the holder byfriction, such that it will not move during the cutting and grindingsteps, but the friction is not so excessive that distortion of thenatural shape of the core would result. The core is secured such thatthe parting line of the core is roughly parallel to the top of theholder. The diameter of the core is measured 90 degrees to thisorientation prior to securing. A measurement is also made from thebottom of the holder to the top of the core to provide a reference pointfor future calculations. A rough cut is made slightly above the exposedgeometric center of the core using a band saw or other appropriatecutting tool, making sure that the core does not move in the holderduring this step. The remainder of the core, still in the holder, issecured to the base plate of a surface grinding machine. The exposed‘rough’ surface is ground to a smooth, flat surface, revealing thegeometric center of the core, which can be verified by measuring theheight from the bottom of the holder to the exposed surface of the core,making sure that exactly half of the original height of the core, asmeasured above, has been removed to within ±0.004 inches. Leaving thecore in the holder, the center of the core is found with a center squareand carefully marked and the hardness is measured at the center markaccording to ASTM D-2240. Additional hardness measurements at anydistance from the center of the core can then be made by drawing a lineradially outward from the center mark, and measuring the hardness at anygiven distance along the line, typically in 2 mm increments from thecenter. The hardness at a particular distance from the center should bemeasured along at least two, preferably four, radial arms located 180°apart, or 90° apart, respectively, and then averaged. All hardnessmeasurements performed on a plane passing through the geometric centerare performed while the core is still in the holder and without havingdisturbed its orientation, such that the test surface is constantlyparallel to the bottom of the holder, and thus also parallel to theproperly aligned foot of the durometer.

Hardness points should only be measured once at any particular geometriclocation.

It should be understood that there is a fundamental difference between“material hardness” and “hardness as measured directly on a golf ball.”For purposes of the present disclosure, material hardness is measuredaccording to ASTM D2240 and generally involves measuring the hardness ofa flat “slab” or “button” formed of the material. Hardness as measureddirectly on a golf ball (or other spherical surface) typically resultsin a different hardness value. This difference in hardness values is dueto several factors including, but not limited to, ball construction(i.e., core type, number of core and/or cover layers, etc.), ball (orsphere) diameter, and the material composition of adjacent layers. Itshould also be understood that the two measurement techniques are notlinearly related and, therefore, one hardness value cannot easily becorrelated to the other.

When numerical lower limits and numerical upper limits are set forthherein, it is contemplated that any combination of these values may beused.

All patents, publications, test procedures, and other references citedherein, including priority documents, are fully incorporated byreference to the extent such disclosure is not inconsistent with thisinvention and for all jurisdictions in which such incorporation ispermitted.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by those ofordinary skill in the art without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the examples and descriptions setforth herein, but rather that the claims be construed as encompassingall of the features of patentable novelty which reside in the presentinvention, including all features which would be treated as equivalentsthereof by those of ordinary skill in the art to which the inventionpertains.

What is claimed is:
 1. A golf ball comprising a core and a cover,wherein the core consists of: a solid inner core layer formed from anunfoamed thermoplastic composition and having a diameter of 1.10 inch orless and a center Shore C hardness (H_(center)) of 50 or less, one ormore optional intermediate core layers, and an outer core layer formedfrom an thermoset composition and having a thickness of 0.200 inches orgreater and an outer surface Shore C hardness (H_(outer surface)) of 70or greater, wherein H_(outer surface)>H_(center), andH_(outer surface)−H_(center)≧40.
 2. The golf ball of claim 1, whereinH_(outer surface)−H_(center)≧45.
 3. The golf ball of claim 1, whereinH_(outer surface)−H_(center)≧50.
 4. The golf ball of claim 1, whereinH_(outer surface)−H_(center)≧55.
 5. The golf ball of claim 1, whereinH_(outer surface)−H_(center)≧60.
 6. The golf ball of claim 1, whereinthe inner core layer has an inner core interface Shore C hardnessH_(inner core interface) such that−5≦H_(inner core interface)−H_(center)≦5.
 7. The golf ball of claim 1,wherein the outer core layer has an outer core interface Shore Chardness H_(outer core interface) such thatH_(outer core interface)−H_(inner core interface)≦H_(outer surface)−H_(center).8. The golf ball of claim 1, wherein the outer core layer has an outercore interface Shore C hardness H_(outer core interface) such thatH_(outer core interface)−H_(inner core interface)>H_(outer surface)−H_(center).9. The golf ball of claim 1, wherein the thermoplastic compositioncomprises at least one of ionomers; non-ionomeric acid polymers;polyurethanes, polyureas, and polyurethane-polyurea hybrids;polyester-based thermoplastic elastomers; polyamides, copolymers ofionomer and polyamide, polyamide-ethers, and polyamide-esters;ethylene-based homopolymers and copolymers; propylene-based homopolymersand copolymers; triblock copolymers based on styrene andethylene/butylene; derivatives thereof that are compatibilized with atleast one grafted or copolymerized functional group; and combinationsthereof.
 10. The golf ball of claim 1, wherein the thermoset compositioncomprises a rubber-based composition comprising at least one of naturalrubber, polybutadiene, polyisoprene, ethylene propylene rubber (EPR),ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber, butylrubber, halobutyl rubber, polyurethane, polyurea, acrylonitrilebutadiene rubber, polychloroprene, alkyl acrylate rubber, chlorinatedisoprene rubber, acrylonitrile chlorinated isoprene rubber,polyalkenamer, phenol formaldehyde, melamine formaldehyde, polyepoxide,polysiloxane, polyester, alkyd, polyisocyanurate, polycyanurate,polyacrylate, and combinations thereof.
 11. A golf ball comprising acore and a cover, wherein the core consists of: a solid inner core layerformed from an unfoamed thermoplastic composition and having a diameterof 1.10 inch or less and a center Shore C hardness (H_(center)) of 40 orless, one or more optional intermediate core layers, and an outer corelayer formed from an thermoset composition and having a thickness of0.200 inches or greater and an outer surface Shore C hardness(H_(outer surface)) of 75 or greater, whereinH_(outer surface)>H_(center), and H_(outer surface)−H_(center)≧50. 12.The golf ball of claim 11, wherein H_(outer surface)−H_(center)≧55. 13.The golf ball of claim 11, wherein H_(outer surface)−H_(center)≧60. 14.The golf ball of claim 11, wherein H_(outer surface)−H_(center)≧65. 15.The golf ball of claim 11, wherein H_(outer surface)−H_(center)≧70. 16.The golf ball of claim 11, wherein the inner core layer has an innercore interface Shore C hardness H_(inner core interface) such that−5≦H_(inner core interface)−H_(center)≦5.
 17. The golf ball of claim 11,wherein the outer core layer has an outer core interface Shore Chardness H_(outer core interface) such thatH_(outer core interface)−H_(inner core interface)≦H_(outer surface)−H_(center).18. The golf ball of claim 11, wherein the outer core layer has an outercore interface Shore C hardness H_(outer core interface) such thatH_(outer core interface)−H_(inner core interface)>H_(outer surface)−H_(center).19. The golf ball of claim 11, wherein the thermoplastic compositioncomprises at least one of ionomers; non-ionomeric acid polymers;polyurethanes, polyureas, and polyurethane-polyurea hybrids;polyester-based thermoplastic elastomers; polyamides, copolymers ofionomer and polyamide, polyamide-ethers, and polyamide-esters;ethylene-based homopolymers and copolymers; propylene-based homopolymersand copolymers; triblock copolymers based on styrene andethylene/butylene; derivatives thereof that are compatibilized with atleast one grafted or copolymerized functional group; and combinationsthereof.
 20. The golf ball of claim 11, wherein the thermosetcomposition comprises a rubber-based composition comprising at least oneof natural rubber, polybutadiene, polyisoprene, ethylene propylenerubber (EPR), ethylene-propylene-diene rubber (EPDM), styrene-butadienerubber, butyl rubber, halobutyl rubber, polyurethane, polyurea,acrylonitrile butadiene rubber, polychloroprene, alkyl acrylate rubber,chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber,polyalkenamer, phenol formaldehyde, melamine formaldehyde, polyepoxide,polysiloxane, polyester, alkyd, polyisocyanurate, polycyanurate,polyacrylate, and combinations thereof.